1. Field of the Invention
This invention relates to filters for cigarettes. In one aspect it relates to a recessed filter with ventilating air means therein. In another respect the invention relates to a filter for a cigarette having air flow accelerating means therein in combination with ventilating air means.
2. Description of the Prior Art
It is well known in the art to add filters to cigarettes wherein the filters are provided with ventilating means to bring ambient air into the filter to dilute the smoke stream. The dilution of the smoke stream reduces the quantity of smoke particulates as well as gas phase components which are delivered to the mouth of the smoker. A number of means have been proposed and are utilized for introducing ventilating air into the cigarette. For example, the wrapper for the tobacco in a cigarette can be made from a porous material which allows for introduction of air along the entire length of the cigarette where it mixes with the smoke stream passing therethrough, thereby diluting the smoke in the stream. Also, the cigarette wrapper may be perforated at selected locations along the length of the cigarette which provides ports for the cigarette through which ventilating air enters. Even further, it is known to perforate the wrapper of the filter for dilution of the smoke stream. There have also been a number of suggestions for incorporating grooves within the filter plug for the cigarette in order to facilitate the addition of ventilating air into the smoke stream.
For example, U.S. Pat. No. 3,596,663 relates to a tobacco smoke filter provided with a corrugated porous plug wrap surrounding a filter element which is circumscribed by a tipping paper having flow-through perforations therein whereby ventilating air enters directly into the filter element or progresses down the grooves to the smoker's mouth. Other patents which relate to cigarette filters having grooves circumscribing the filter element for the introduction of ventilating air into the filtering end of the filter cigarette include U.S. Pat. No. 3,577,995; U.S. Pat. No. 3,572,347; U.S. Pat. No. 3,490,461; U.S. Pat. No. 1,718,122; U.S. Pat. No. 3,788,330; U.S. Pat. No. 3,773,053; U.S. Pat. No. 3,752,165; U.S. Pat. No. 3,638,661; U.S. Pat. No. 3,608,561; West German Pat. No. 2,302,677; British Pat. No. 1,414,745; British Pat. No. 1,360,612; British Pat. No. 1,360,611; and, U.S. Pat. No. 3,910,288, the aforementioned British patents being directed to non-wrapped acetate filters. Furthermore, there are a number of patents directed to the incorporation of centrally disposed tubes into a cigarette filter. These include, for example, U.S. Pat. No. 3,860,011; U.S. Pat. No. 4,037,524; U.S. Pat. No. 4,086,846; U.S. Pat. No. 4,022,221; U.S. Pat. No. 3,045,680; U.S. Pat. No. 3,621,851; U.S. Pat. No. 3,674,036; U.S. Pat. No. 4,109,666; and U.S. Pat. No. 4,256,122. Further, U.S. Pat. No. 4,380,241 relates to a non-filtering cigarette mouthpiece including a centrally disposed smoke flow tube.